Subject: CVE-2024-26740: net/sched: act_mirred: use the backlog for mirred ingress

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_mirred: use the backlog for mirred ingress

The test Davide added in commit ca22da2fbd69 ("act_mirred: use the backlog
for nested calls to mirred ingress") hangs our testing VMs every 10 or so
runs, with the familiar tcp_v4_rcv -> tcp_v4_rcv deadlock reported by
lockdep.

The problem as previously described by Davide (see Link) is that
if we reverse flow of traffic with the redirect (egress -> ingress)
we may reach the same socket which generated the packet. And we may
still be holding its socket lock. The common solution to such deadlocks
is to put the packet in the Rx backlog, rather than run the Rx path
inline. Do that for all egress -> ingress reversals, not just once
we started to nest mirred calls.

In the past there was a concern that the backlog indirection will
lead to loss of error reporting / less accurate stats. But the current
workaround does not seem to address the issue.

The Linux kernel CVE team has assigned CVE-2024-26740 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 4.10 with commit 53592b364001 and fixed in 6.6.19 with commit 7c787888d164
	Issue introduced in 4.10 with commit 53592b364001 and fixed in 6.7.7 with commit 60ddea1600bc
	Issue introduced in 4.10 with commit 53592b364001 and fixed in 6.8 with commit 52f671db1882

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26740
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/sched/act_mirred.c
	tools/testing/selftests/net/forwarding/tc_actions.sh

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/7c787888d164689da8b1b115f3ef562c1e843af4
	https://git.kernel.org/stable/c/60ddea1600bc476e0f5e02bce0e29a460ccbf0be
	https://git.kernel.org/stable/c/52f671db18823089a02f07efc04efdb2272ddc17